The Warm Neptune GJ 3470b Has a Polar Orbit
Abstract

The warm Neptune GJ 3470b transits a nearby (d= 29 pc) bright slowly rotating M1.5-dwarf star. Using spectroscopic observations during two transits with the newly commissioned NEID spectrometer on the WIYN 3.5 m Telescope at Kitt Peak Observatory, we model the classical Rossiter–McLaughlin effect, yielding a sky-projected obliquity of$λ=98−12+15◦$and a$vsini=0.85−0.33+0.27kms−1$. Leveraging information about the rotation period and size of the host star, our analysis yields a true obliquity of$ψ=95−8+9◦$, revealing that GJ 3470b is on a polar orbit. Using radial velocities from HIRES, HARPS, and the Habitable-zone Planet Finder, we show that the data are compatible with a long-term radial velocity (RV) slope of$γ̇=−0.0022±0.0011ms−1day−1$over a baseline of 12.9 yr. If the RV slope is due to acceleration from another companion in the system, we show that such a companion is capable of explaining the polar and mildly eccentric orbit of GJ 3470b using two different secular excitation models. The existence of an outer companion can be further constrained with additional RV observations, Gaia astrometry, and future high-contrast imaging observations. Lastly, we show that tidal heating from more »

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Award ID(s):
Publication Date:
NSF-PAR ID:
10367476
Journal Name:
The Astrophysical Journal Letters
Volume:
931
Issue:
2
Page Range or eLocation-ID:
Article No. L15
ISSN:
2041-8205
Publisher:
DOI PREFIX: 10.3847
National Science Foundation
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